In a perimetry (threshold value examination), it is possible to obtain sensitivity for light stimulation in each retina part, and it is possible to judge a progress of a disease in glaucoma by confirming the change of such a sensitivity over time.
In many perimetry, a difference between the normal value in each examination point and the examination result is computed and the means value of the computed values is used as an index (MD slope and the like). Such a mean value may be a simple mean value of the whole visual field, or may be weighting mean value by preparing the weighting factor in each portion of the visual field (in a conventional perimeter, the dispersion of the normal eye data in each portion is determined as the weighting factor).
The reason for adopting such a weighting factor is that the center of the visual field is more important than the peripheral portion thereof and its importance is different even in the same depression of 1 dB. The weighting factor may be computed from the standard deviation of the normal data as the conventional perimeter, or a ratio to the decibel value till the percentile designated from the normal value. The same result is obtained in the former and the latter if the data shows a normal distribution, but the latter is considered to be useful in the distribution where the area is wide on the side of the lower values as the peripheral portion of the visual field since the actual distribution can be reflected.
Furthermore, at the initial stage of the glaucoma, the sensitivity depression is seen in a part of the retina not but the whole thereof, and the area broadens with the progress of the disease. For this reason, there is a perimeter for indicating the change with time in each examination point. A function of such a product is to indicate the change with time in each portion of the visual field and to search whether statistically significant depression can be seen in each regression. There is such a report that the progress can be grasped by the MD (mean deviation), in which only portion showing significant depression is extracted, faster than the change with time of the whole MD value.
However, the following problems remain at the present.    (1) In the judgment of the progress, one that obtains the statistically significant inclination is extracted, but it is not always the portion showing the glaucoma-related structural abnormality.    (2) Severity of the depression in each point is not considered (all depressions are evaluated with the same standard).
Then, the proposed system is that a concerned area is designated from the perimetry result and the change with time for the concerned area is computed and measured (patent related document 1).